The present invention relates to a process and system for collecting data about roads located in a geographic area and using the collected data to develop representations of the positions and shapes of the roads for a geographic database.
Geographic databases have various uses. Geographic databases are used in in-vehicle navigation systems, personal computers, networked computing environments, and various other kinds of platforms, as well as Internet applications. Geographic databases are used with various kinds of applications to provide many different functions, including map display, route calculation, route guidance, truck fleet deployment, traffic control, electronic yellow pages, emergency services, and so on. Geographic databases are also used with various types of drivers"" assistance features such as obstacle warning and avoidance, curve warning, advanced cruise control, headlight aiming, and so on.
In order to provide these kinds of functions, a geographic database includes data that represent physical features in a covered geographic region. Physical features that are represented by geographic databases include roads, points of interests, railroad tracks, bodies of water, intersections, and so on. With respect to navigable roads, geographic databases may include data about the various characteristics of the represented roads, such as the geographic coordinates of roads, speed limits along road segments, locations of stop lights, turn restrictions at intersections of roads, address ranges, street names, and so on. Geographic databases may also include information about points of interest in covered regions. Points of interest may include restaurants, hotels, airports, gas stations, stadiums, police stations, and so on.
Collecting information for a geographic database is a significant task. Not only is the initial collection of information a significant undertaking, but a geographic database needs to be updated on a regular basis. For example, new streets are constructed, street names change, traffic lights are installed, and turn restrictions are added to existing roads. Also, new levels of detail may be added about geographic features that are already represented in an existing geographic database. For example, existing data about roads in a geographic database may be enhanced with information about lane widths, shoulder sizes, lane barriers, address ranges, sidewalks, bicycles paths, etc. Thus, there exists a need to continue to collect information for a geographic database.
Included among the most important types of data in a geographic database are the positions and geometry (i.e., shapes) of roads. Using a GPS system, a person can determine his/her geographic coordinates on the surface of the earth. However, in order for the person to know what road he/she is on, it is required to know the geographic coordinates of the roads around the person in order to relate the person""s geographic coordinates to the geographic coordinates of the roads.
How a geographic database represents the positions and geometry of roads is an important consideration that can affect the usefulness of the geographic database. The manner in which roads are represented in a geographic database can affect the kinds of applications that can use the data in the geographic database.
Geographic databases represent positions of roads by identifying the geographic coordinates of points along the roads. According to a prior method, a geographic database developer-technician performed the step of selecting points along a road to be used to represent the road in a geographic database. The geographic database developer-technician viewed an image of the road and, while viewing the image, estimated the locations of points from the image to use to represent the road.
The image of the road that was viewed by the database developer-technician could be obtained by various means. One way to obtain an image of the road was to use aerial photographs of the roads. Another way to obtain an image of the road is to view a trace of GPS data acquired while driving along the road. Still another way to obtain an image of the road was to use ground-based photographs. Regardless of the means by which the image of the road was obtained, the geographic database developer-technician selected points from the image of the road and the geographic coordinates of these points were used to represent the road in the geographic database. For straight road segments, the database developer-technician identified the geographic coordinates of the intersections at each end of the straight road segment. For a curved road segment, the database developer-technician selected one or more points along the curved portion of the road segment to approximate the location of the road.
Although this process worked well, there is room for improvement. Aerial photographs, as well as other images from which points along roads could be selected, provide only a limited amount of detail. In addition, aerial photographs and other kinds of images of roads are useful for acquiring only certain kinds data about geographic features. For example, aerial photographs of roads are not useful for identifying the locations of road signs or address ranges along the roads. Thus, if an aerial photograph is used to determine the geographic coordinates of locations on roads, it is still necessary for a geographic database developer-technician to physically travel along the road segments shown on the aerial photograph to acquire data about the features that cannot be discerned from the aerial photograph. This increases the cost of acquiring information for a geographic database. Similar limitations are associated with images obtained by other means.
Another area in which there is room for improvement relates to consistency. When an image of a road is used to determine points along the road to represent the road, the selection of points depends to some extent upon the judgment of the geographic database developer-technician. Therefore, the points chosen to represent a road may not be consistent between different geographic database developer technicians. This is especially the case for curved portions of roads.
Accordingly, there exists a need for an improved process to collect data about the locations of physical features for a geographic database. In addition, there exists a need for an improved process and/or system to collect data about positions and shapes of roads and use the collected data to represent the roads in a geographic database.
To address these and other objectives, the present invention comprises a process and system for collecting data about roads located in a geographic area and using the collected data to develop representations of the positions and geometry of the roads for a geographic database. The data are collected using equipment installed in a vehicle that is driven on the roads. The data that are collected may represent different properties of the roads. The data that are collected may include data that represent the vehicle""s approximate positions (i.e., geographic coordinates) along the roads at particular times. The data that are collected also may include data representing the vehicle""s acceleration and speed at particular times. The data collected while traveling may be fused and smoothed. The data collected while traveling are processed by a program that automatically selects which of the data are necessary to provide a specified level of accuracy in a geographic database that includes data that represent the roads including data that represent positions and/or geometry of the roads. The data selected by the program are stored in the geographic database.